A variety of systems and applications use stacks of sheets, or plates, or both, which may be made of metal, paper, plastic, and the like. Printing plates (hereinafter singly or collectively referred to as “plates”) are typically stacked on plate pallets, which house the plates and facilitates their protection, transportation, and handling.
A system for handling printing plates will generally use cassettes having specific dimensions for a limited number of plates, for example 30-50 plates. Cassettes can usually be set to contain plates of various sizes, but all plates in the same tray are of one size. The plates may be manually removed from the plate pallets and inserted into the cassettes for use by the plate imaging system. Plates packed in plate pallets are separated by intermediate paper sheets, hereinafter referred to as separation paper.
Cassettes containing printing plates are both heavy and bulky, and moving such trays requires complicated and expensive mechanisms and is time consuming; specifically, during the loading of the plates from the plate pallets into the cassettes. There is a widely recognized need for an automatic and efficient handling system for feeding plates directly from the original plate pallet into the imaging device, while maintaining precise alignment of the plates during the plate feeding process. This need is addressed by the invention described in commonly-assigned U.S. patent application Ser. No. 12/045,058.
The plate stacks received from plate manufacturers often comprised of at least 600 plates. Each plate is separated from the next by a separation paper, and the entire stack of plates is on a plate pallet for a job requiring a number of plates of the same size, loading plates from a plate pallet to an imaging device is preferred to loading plates from a cassette. Plates may shift or fall from their original position, however, during transportation of the pallet into the plate loading device or during the loading process of plates into the imaging unit. The shift can occur also during shipping of the plate stacks from the manufacturer to the end user. Thus, there may be some drawbacks to loading an imaging device exclusively from a plate pallet.
The invention provides a solution for facilitating plate loading into an imaging device through an automatic plate loader (APL), capable of loading plates directly from plates in a plate pallet, as well as from plates that are fetched from plate cassettes.